This invention relates to a hydraulic pressure control apparatus including a solenoid valve arranged to adjust an opening degree in accordance with a command current, and to control to increase or decrease a hydraulic pressure.
Conventionally, in case of a solenoid valve to control a hydraulic pressure, a hysteresis is generated in a driving current of a solenoid and an output pressure on an increasing side and a decreasing side of the current. As a countermeasure against this, an actual measurement map is formed from an actual measured value of the output pressure at each current value when the current value increases to maximize the output pressure and then the current value decreases to zero. A current average value between the increasing side current value and the decreasing side current value which correspond to the same output pressure measured value on the measurement map is calculated. A map representing a relationship between the calculated current average value and the output pressure measured value is formed. The driving current of the solenoid is controlled by using this map (cf. for example, U.S. Pat. No. 6,751,542 (corresponding to Japanese Patent Application Publication No. 2003-294126)).